Method of treating dry cell containers



Patented Sept. 22, 1931 oTTo nnnonnnnn enonen n. sonnonnim- F wAusAU', WISCONSIN, nss'ienons.

PAT NT "OFFICEJCI .TO MARATHON BATTERY COMPANY, OF WAUSAU, WISCONSIN, A CORPORATION OF WISCONSIN No'IDra wing.

Thisinven tion relates to a new andimproved methodof treating dry cell contain ers, and more particularly to a methodof treating the zinc canffor dry cells to prevent '5 deterioration-of the can, bothljwhil'e awaiting use and during use." i

A source of considerable lossjof energy and efliciency ofddrypcells lies'intlie fact that, as generally"constructed there is a 10 considerable deterioration ofthe cells both while simply being lieldin stock awaiting use and while being discliarged-nta light intermittent rate, such for example, as. that" to which a radio A or B batteryis subjected. This [deteriorationconsists largely in' the corrosion of thezinc container of the 0e11,.

which container forms the negative electrode of the cellf i i We are aware of the fact that'it has been practice with some manufacturers to treat the zinc electrodes with mercury or certain.

9 of a dry cell container, whibhare' subject to corrosion, may be pr tectedmqre satisfactorily than heretofore, by a coating. of e cu y It is a further object tiopifovidefa method of this characteninfwhich the coating may be uniformly and certainly applied without,

the use of complicated machinery. v

It is also an object top'rovide a method whereby the coating may be appliedwithout the material loss of, the mercury salts used in the process. f" U i The employment of solutions for coating zinc cans with mercury byl proces ses other than that ofthe present invention, is sub-Y ject to many difliculties,due to the fact that the valuable nature of the solutionsmakes it necessary-to use themgoverfand over again and after each use, 'the'concentration of the solution of the 'mercur salmhe zinc chloride 9. content and acidity are altered. If the solu METHOD on TREATING DRYY CELL coNTAINEns A :,:A Pp1ication;fi1er1 M4,. 1928. serial No. 275,254.,

tionis to be restored to a known and workable" condition, coiriplicated analyses and methods of replenishing the mercury de-v ostm n the zinc ,are'necessary. In additionto this objection, the use of such solutions requiresclose control of the tempera ture of the, amalgamating bath and the length of time during which the zinc isin contact with the mercury containing-solution. It is therefore affurther. object of the present invention to provide a method in which the solution 1s used once andis then discarded without loss and furthermore; one, which does. not require theemployment of skilled workmen nor any special degree'of skill whatsoever. In accordance with the present process, the solution is merely, placed in the containers to be coated and left for a period of time ,suflicientto complete the coating action, after which the remaining solutionis discarded. The presentprocess further'permits accurate and predetermined results; and absolute uniformity in the coating results of difierent operations. v ,Other and furtherobjects will appear-as the description proceeds. i The methods of adding the mercury com pound to either the gelatinizable electrolyte or: thedepolarizing mixturedo not rotect the can above the. initial heights '0 these parts of the cell. It is well known that the electrolyte expands sometimes while the cell is idle andalwayswhile it is being discharged. As the electrolyte expands it rises in the cell and comes in contact withthe unamalgamated zincif the mercury compoundhas merely been included in the e1ectrolyte. paste. I

. According to our. improved method a mercury containing solution is poured into the can toifillthe canto a point abovethat which will be reachedby the mixture to be later placed in the can in assembling the cell. Inthismanner the zinc is protected where evergthejelectrolyte may contact with it during the life of the cell. a v It should be understood that in the employment of solutionsof mercury, salts for coatin flarticles such as zinc cans; thatif the concentration such that the coating ac tion may be accomplished in a relatively tion, if a 6% solution ofmercury chloride" is used, a quantity of mercury is deposited on the zinc can in thlrty seconds,render1ng the can unfit for vuse as dry cell containers.

- sufficientmercuryis left in the solution after Thecan would beso weakened, that it would be crushed like an eggshell and would not have sufficient strength'to act as a supporting'container nor withstand the force of the spring contact ng connector, without puncture. On the other hand, if solutions of much lesser concentration, though of the same order of magnitude, namely, 1% solution is' used, the time required to deposit a satisfactory coating of mercury may be increased to approximately three minutes. Although it is possible'to amalgamate dry cell cans in this manner, by solutions of this concentration,. the process is subjectto the objections above referred to, namely, that the completion of'tlie coating operation, to

render'it necessary to re-use' thesolution to prevent waste. Unless solutions of known concentration areemployed, no satisfactory degree of control can be exercised and therefore, it becomes necessary to analyze; the solution and resort to some means for restoring itsi'con'centration. This pr'ocessis further subject to control by the operator as the coating process is still in'operation when it becomes necessary to discontinue the treatment.

The applicants have discovered that the difliculties herein .aboveenumerated may be eliminated if solutions of relatively weak concentration are employed, the concentration of which is calculated and selected as that which, when completely exhausted of its mercury content, will supply the exact coating which desired for the dry cell cans. 'By use'of the weak "solution, the

period of treatment is of course, prolonged,

butan over-treatment results-in no harm" as the coating operation automatically comes to an end upon completion ofthe coating operation, that'is' to say; upon'exposure for a suflicient' length of time. Thesolutions which' are now. devoid of mercury-may; be

all operations will produce exactly the; same resultsf and consequently"uniform products.

tion automaticaly runs to completion and completely exhausts itself at exactly the point where the cans have received the desired coating.

As a spec fic example, a satisfactory coating for a flashlight. or radio'cell, one and one-- quarter (1 A) inches in diameter and two and one-quarter (2 4) inches in height,

may be obtained by using' ten milligrams of mercury bichloride in a quantity of solution adapted to fill such a canto the desired height. It has been found in practice that the mercury is practically completely removed from "the solution in a few hours. The solution may, therefore, be discarded afterbeing once used Without any material lossof mercury salts. V

' satisfactory coating may also be obtained by filling cans of the above-mentioned size, tothe desired height, with a one per cent solution oflmercury bichloride, and allowing it to remain thereinv for approximately three minutes. The cans are then emptied and are ready for use. The solution may be strengthened by adding about ten (10) milligrams of mercury bi chloride for each cell treated, and the solution reused; Thelsolution may be merely a neutral solution of the mercury compound or the solution may be sli 'htly acidified with a suitablgi acid, such' or example, as muriatic acl This method of procedure hasbeen fully tried out and cells'treatedin this manner have been found to have a very materially upon the inner walls of the cell container.

'2. The method of treating zinc dry cell containers which comprises selecting ,a so lution'of a mercury salt of a concentration calculated to produce the desired finished coating upon complete exhaustion of the mercury, placing said solution in said containers and depositing upon the inner walls 7 mercury content of said solution. discarded without 'waste. By commencing with a solution of the same concentration,

this 20th day requires no unusualcare or skill sthe soluof said containers,substantially all of the his iio 

